This invention relates to a bobbin lead roving machine and more particularly to a method and apparatus for controlling the winding tension of the roving through adjustment of the bobbin r.p.m.
In a roving machine, the rate of increase in the bobbin diameter corresponding to increases in the number of roving layers on the bobbin is changed with changes in the roving conditions such as weight and kind of fibers, flyer r.p.m. or the number of twists. Hence, with a control method making use of a single set of cone drums, it is difficult to adjust the machine base so that the winding tension may be constant under all spinning conditions from the start of winding until the bobbin is full. Since fluctuations in the roving tension may cause fluctuations in roving weight and hence in the number of deniers of the resulting roving, high skill and experience are required of the operator to effect an adjustment of the roving tension.
Various mechanical devices have been proposed for realizing constant roving tension, such as roving tension correcting devices described in the Japanese Patent Publication No. 48652/1977 and the Japanese Utility Model Publication No. 13376/1977 in connection with a roving machine making use of cone drums as the means for changing the bobbin r.p.m. With these devices, a trial or tentative spinning operation is effected under given spinning conditions and the compensation or correcting system is manually set while the operator checks the roving travelling from the front roller to the flyer top as to tautness several times from the start of winding on the bobbin until the bobbin is full. This system is not completely satisfactory since the setting operation is complex and need be performed at several check points.
In order to obviate the manual setting, it is proposed by the Japanese Patent Publication No. 22532/1976 to detect the state of slack in the roving travelling from the front roller towards the flyer top by a photosensitive tube or to detect the deflecting state of the roving for controlling the roving r.p.m. automatically. However, this system is also not satisfactory because of difficulties in the correcting control based on mean values from plural spindles, and the possibility of issuing an erroneous correcting command when the spinning state is met in the single spindle control system. In addition, the numerical relation between the state of slack in the roving and the roving tension is not definite, thus making it difficult to control the bobbin r.p.m. accurately.
The roving machines currently employed are of the bobbin lead type in which the roving is wound on the bobbin on the basis of the difference between the bobbin r.p.m. and the flyer r.p.m. (winding r.p.m.) which is less than said bobbin r.p.m. The roving travelling from the front roller is subjected to a slight elongation (known as indefinite draft) while the roving is supplied through the slot in the main body of the flyer and flyer presser and wound on the bobbin, whilst the roving is twisted by the flyer rotation. Due to such draft, the winding speed of the roving is slightly higher than the spinning speed at the front roller. If a constant roving speed is desired, it is necessary to maintain this indefinite tension constant from the start of winding until the bobbin is full.
It is therefore an object of the present invention to provide a method for automatically maintaining the roving winding tension constant from the start of winding until the bobbin is full, through measuring the indefinite draft applied to the roving for correctly controlling the bobbin r.p.m.